I am using curl and PHP api to get the results from webpagetest.org. When i am running the script for one url it is showing your request pending and sometimes it is taking too long. Could anybody help me is there anyway to get results quickly.

WPT tests go into a priority queue and the tests are run in the order they are submitted (with API tests getting a lower priority than interactive users). If you are submitting tests to a busy location it could take hours before the test is run. Even if you are submitting to a less-busy location it will usually still take several minutes to get a result.

If you want control over the test times and need test results faster (or with guarantees) you need to run a private instance where you have full control over the capacity and testing.